1. Field of the Invention
The present invention relates to a hydraulic modulator for a brake device, and more particularly to a hydraulic modulator for a brake device which can be reduced in size by improving the arrangement of components and the internal structure.
2. Description of Background Art
Conventionally known is a brake system such that in operating a hydraulic brake to reduce a vehicle speed, an oil pressure for operating a brake caliper is obtained by the drive force of an actuator to thereby assist a brake operation by the operator. A device adapted to be applied to such a brake system to generate an oil pressure by using the drive force of the actuator will be hereinafter referred to generally as a hydraulic modulator. The hydraulic modulator capable of performing minute hydraulic control by electronic control of the actuator is suitable for use with an antilock brake system (ABS) for avoiding wheel locking upon braking by intermittently reducing the oil pressure produced in the brake caliper and also suitable for use with a front and rear interlocked brake system for automatically distributing a braking force to the front and rear wheels according to a vehicle running condition such as a vehicle speed.
Japanese Patent Laid-Open No. Hei 1-262244 discloses a hydraulic modulator such that a piston is slidably held in a cylinder for supplying a pressurized brake fluid to a brake caliper and that the piston is connected through a screw mechanism to a rotating shaft of an electric motor. With this configuration, the piston is slid by driving the electric motor to thereby generate an oil pressure required for the operation of the brake caliper.
Japanese Patent Laid-Open No. 2005-212680 discloses a hydraulic modulator such that a rotating shaft of an electric motor and a cylinder for supplying a pressurized brake fluid to a brake caliper extend in perpendicular relationship with each other, that the drive force of the electric motor is transmitted through a speed reducing mechanism to another rotating shaft on which a swing arm is mounted, and that a piston slidably held in the cylinder is slid by the operation of the swing arm.
However, the technique described in Japanese Patent Laid-Open No. Hei 1-262244 has a problem such that the hydraulic modulator tends to be elongated in the axial direction of the rotating shaft of the electric motor because the piston extends on the axis of the rotating shaft of the electric motor. Further, the technique described in Japanese Patent Laid-Open No. 2005-212680 has a problem such that an unwanted space is generated between the electric motor and the cylinder to cause an increase in overall size of the hydraulic modulator because the electric motor and the cylinder as elongated components extend perpendicularly to each other. Accordingly, it is difficult to ensure an installation space for such a conventional hydraulic modulator in a motorcycle limited in extra space, and it is therefore susceptible to improvement in configuring a hydraulic modulator which is compact with a small unwanted space and suitable for use in a motorcycle.
It is accordingly an object of the present invention to provide a hydraulic modulator for a brake device which can be reduced in size by improving the arrangement of components and the internal structure.